Road, sea, air and laboratory speeds
Convert km/h to mph for foreign speed limits, m/s for physics homework or knots for sailing and aviation. Exact factors, instant results.
Speed units split along professional lines: roads use km/h or mph, physics uses metres per second, ships and aircraft use knots. Crossing between them is a daily annoyance for drivers abroad and students alike.
Every factor here is exact. A knot is precisely one nautical mile per hour, which is 1.852 km/h — a definition tied to the size of the Earth rather than an arbitrary standard.
The converted speed across five units, updating live km/h and mph for driving, m/s for physics, knots and ft/s for specialist work Enough precision to compare speed limits without rounding surprises Uses exact definitions: 1 mph = 1.609344 km/h, 1 knot = 1.852 km/h. These are scalar speeds; direction and wind correction are not part of the conversion. How fast is 100 km/h in mph? 62.14 mph. It is the standard motorway limit across much of Europe and roughly 8 mph below the US interstate norm of 70 mph.
Why do ships and planes use knots? One knot is one nautical mile per hour, and a nautical mile is one minute of latitude. Navigating on a chart, speed and position use the same measurement — no conversion needed.
How do I convert m/s to km/h quickly? Multiply by 3.6. Usain Bolt's top speed of about 12.4 m/s becomes roughly 44.6 km/h.
Is mph the same in the US and the UK? Yes, both use the statute mile of 1.609344 km. It is the gallon, not the mile, where the two countries diverge.
Worked example A German autobahn limit
Input: 130 km/h → mph
Output: 80.78 mph
Note: The advisory autobahn speed lands just above the 70 mph limit used across the UK.
